How to add 2nd. A/C

I have a 30 amp fifth wheel. I would like to add a 2nd A/C in the bedroom. A RV dealer told me they could add a 20 amp drop leg. That would be the 2nd ac wired directly to a seperate receptacle mounted on the side of the trailer. I would have to plug in my 30 amp cord like normal and then if I wanted to run my 2nd ac I would have to plug in a extension cord to the seperate receptacle and then plug the cord into the 20amp outlet next to the 30 amp on the park power . Has anyone ever heard of this. That would mean that the parks power would have to be wired for 50 amps total.??????????????????